Chemo-Mechanical Degradation Mechanisms of Shale Minerals Induced by CO2–Water–Rock Interactions: A Targeted Nanoindentation Study under Different CO2 Partial Pressures

Abstract To investigate the chemo-mechanically coupled degradation mechanisms of individual mineral phases during CO2–water–shale interactions, shale samples from the deep-marine Wufeng–Longmaxi Formation in the Sichuan Basin were selected. A series of multiscale characterization techniques, including X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), and targeted nanoindentation tests, were conducted on shale samples subjected to high-temperature and high-pressure static immersion under different CO2 partial pressures. The relative mineral content variations, microstructural morphology evolution, and degradation behaviors of the micromechanical properties of different minerals were comprehensively analyzed. The results show that the acidic environment in the CO2–…